Where legal, I don't think "safety" is an issue beyond the judgment of the individual rider. The problem is to non riders who see someone splitting where illegal, they won't see any difference between 'illegal" and "unsafe".

The only reason I question doing it illegally is the long term effects it may have on all riders. Like with cyclists ,a few people are looking for any excuse to cause us misery on the street or in the law books.
Why ask for trouble?

I'm pretty well convinced that its a matter of 'holyhellfireshit! WTF was that?!' more than it is a safety issue when a MC shares lanes here in the DC area.

Least in the people paying attention.

I'm also convinced that if more people did it (see Houston for an example) that the cagers wouldn't react nearly as erratically. FWI've heard/seen here, Houston MC riders are taking it upon themselves to share lanes in rush hour traffic. I haven't heard of many issues resutling from that.

M

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I'm a cyclist that rides motos, not a moto rider that rides bicycles.

I think this is a major issue. Whatever the limited political influence motorcyclists have is being spent on the idiotic helmet laws and loud pipes.
I remember few years back, after a garbage truck driver on drugs killed 5 bikers, a couple of counties in Arizona tested filtering at the traffic lights. I don't know what came out of this.

Not sure if I already posted here, but here's the situation in Arizona:

After that specific accident, the state researched the safety factors of lane sharing. A proposal was drawn up, to allow a 1 year "trial" period in Maricopa County (the greater Phoenix area). The proposal passed through the house and the senate with flying colors. Just before it was to go into effect, the governor (Jan Brewer) shot it down, ignoring all the statistics, saying that it "looks dangerous".

Highway patrol and local police fully understand that it's a load of crap, and that motorcyclists stuck in traffic (especially mid-Summer) run a high risk of overheating. So, while it's still illegal, it's somewhat accepted. If you're doing it in an unsafe manner, you'll get stopped. You'll also get stopped if doing it through traffic that's moving. Motorcycles also get HOV lane privileges, which helps keep riders (and bikes) cool.